In September 2021, as the world searched for an exit from pandemic emergency, a leading infectious disease specialist at Duke-NUS Medical School offered a quiet but consequential reframing: not every positive test tells a story worth chasing. Prof Ooi Eng Eong argued that tracking asymptomatic COVID cases consumes resources without proportionate public health return, and that herd immunity — long held as the pandemic's promised horizon — was never truly within reach. What remained, he suggested, was not a finish line but a long road of management, with vaccination as the most reliable companio
Expert Questions Value of Tracking Asymptomatic Covid Cases
Herd immunity is not achievable with a virus that mutates and reinfects
Mark
Why does it matter whether we track asymptomatic cases? Aren't more data points always better?
Mimi
Not necessarily. If someone has no symptoms and isn't driving hospitalizations, knowing they're infected tells us very little about disease burden. It's like counting every car that passes a highway—the number is interesting, but it doesn't tell you about traffic flow or accidents.
Mark
But couldn't asymptomatic people still spread the virus to others?
Mimi
They could, yes. But by September 2021, most people had either been vaccinated or exposed. The question became: are we spending resources to prevent transmission that's already happening anyway, or are we preventing severe disease? Those are different goals.
Mark
You mentioned herd immunity is a myth. What did you mean by that?
Mimi
Classical herd immunity assumes the virus stops circulating once enough people are immune. But COVID mutates constantly and immunity wanes. You can't reach a point where it simply disappears. It becomes endemic—present, managed, but not eliminated.
Mark
So vaccination doesn't end the pandemic?
Mimi
Vaccination prevents severe illness and death. That's enormous. But it doesn't create a finish line where we all go back to normal and never see COVID again. We're learning to live with it, like we do with flu.
Mark
How does dengue fit into this?
Mimi
Dengue is endemic in this region. We don't eliminate it. We manage it, reduce severe cases, and accept that some transmission will happen. COVID may follow that same path—not eradication, but coexistence.
The Pulse
- Health systems worldwide were drowning in case count data, and a respected expert was asking aloud whether much of it actually mattered.
- The cherished goal of herd immunity was declared a myth — a significant rupture with the narrative that had sustained public patience through months of sacrifice.
- Asymptomatic surveillance, once treated as essential, was recast as a potential misallocation of finite public health resources.
- Vaccination was repositioned not as a cure or an endpoint, but as a permanent tool for reducing death and severe illness in an endemic future.
- Countries were already quietly shifting from infection counts to hospitalization metrics, and Ooi's argument gave intellectual grounding to that drift.
- The conversation pointed toward a harder, more honest reckoning: the pandemic would not end, but the way societies chose to live within it could still be shaped.
In September 2021, as the world searched for an exit from pandemic emergency, a leading infectious disease specialist at Duke-NUS Medical School offered a quiet but consequential reframing: not every positive test tells a story worth chasing. Prof Ooi Eng Eong argued that tracking asymptomatic COVID cases consumes resources without proportionate public health return, and that herd immunity — long held as the pandemic's promised horizon — was never truly within reach. What remained, he suggested, was not a finish line but a long road of management, with vaccination as the most reliable companion for the journey.
In mid-September 2021, as vaccination campaigns accelerated and governments searched for a new footing with COVID-19, Prof Ooi Eng Eong of Duke-NUS Medical School posed a pointed question in a Straits Times Health Check podcast: what is actually gained by tracking people who feel perfectly well?
Ooi's argument was measured but direct. Reporting asymptomatic infections — positive tests with no accompanying illness — offered limited practical value, he contended. The resources devoted to identifying and monitoring these individuals might serve public health better if redirected. This was not a call to lower vigilance, but a strategic challenge to what the pandemic had trained everyone to count.
He went further, dismantling another pillar of pandemic hope: herd immunity. Unlike diseases that confer lasting, sterilizing immunity, COVID-19 would continue to mutate and reinfect. The classical threshold — where enough immune bodies in a population stop a virus in its tracks — was, in his view, unachievable. The virus would persist.
What could be achieved was sustained vaccination, understood not as a cure but as an ongoing means of keeping severe illness and death at bay. Ooi drew on regional experience with dengue to illustrate the point: endemic diseases can be managed, integrated into public health systems, and lived with — even when they cannot be eliminated.
His perspective arrived as health authorities were already quietly reconsidering their metrics, with some nations moving away from daily case tallies toward hospitalization figures. Whether policymakers would follow the logic of his argument — and reshape surveillance and communication strategies accordingly — remained the open question.
In mid-September 2021, as vaccination campaigns ramped up across the globe and countries grappled with how to manage COVID-19 as an ongoing threat rather than an acute emergency, an infectious disease specialist at Duke-NUS Medical School offered a provocative question: why spend resources tracking people who don't feel sick?
Prof Ooi Eng Eong, who leads the Programme in Emerging Infectious Diseases, sat down with Joyce Teo, a senior health correspondent at The Straits Times, to discuss the pandemic's trajectory and the role vaccination would play in moving forward. The conversation, recorded for the Health Check podcast, centered on a tension that had been building in public health messaging for months: the obsession with case counts, particularly asymptomatic infections, and whether that focus actually served public health or merely created noise.
Ooi's core argument was direct. Reporting unlinked cases or asymptomatic infections—people who tested positive but showed no symptoms—had limited practical value. The energy spent identifying and tracking these individuals, he suggested, might be better directed elsewhere. This was not a call to ignore COVID entirely, but rather a recalibration of where attention and resources should flow. In a pandemic that had already consumed enormous amounts of public and private capacity, the question of what to measure and report had become a strategic one.
Beyond case tracking, Ooi addressed another concept that had dominated pandemic discourse: herd immunity. The idea that a population could reach a threshold of immunity—through infection or vaccination—where the virus could no longer spread freely had become a kind of holy grail for some policymakers and a rallying cry for others. Ooi rejected it as myth. COVID-19, he argued, would not behave like diseases that confer lasting, sterilizing immunity. The virus would persist, mutate, and reinfect. Herd immunity, in the classical sense, was not achievable.
What was achievable, in his view, was vaccination. Not as a one-time intervention that would end the pandemic, but as an ongoing tool to reduce severe illness and death. This framing—vaccination as management rather than cure—represented a significant shift from the earlier pandemic narrative, when vaccines were sometimes presented as the finish line. By September 2021, with delta variants circulating and breakthrough infections occurring in vaccinated populations, that framing had become more realistic.
Ooi also drew on historical precedent. Dengue outbreaks in the region offered lessons about how endemic diseases could be managed without eliminating them entirely. The parallel suggested that COVID might follow a similar arc: from pandemic to endemic, from emergency response to integrated disease management. The question was not how to eradicate the virus, but how to live with it while minimizing harm.
The podcast episode landed at a moment when health authorities worldwide were making real decisions about surveillance, reporting, and communication. Some countries were moving away from daily case counts. Others were shifting focus from infections to hospitalizations. The debate over asymptomatic cases—whether to test for them, report them, isolate around them—had become genuinely contentious. Ooi's perspective, coming from someone with deep expertise in emerging infectious diseases, offered intellectual cover for a reorientation that many public health systems were already considering. The question now was whether policymakers would act on it.
Notable Quotes
Reporting unlinked or asymptomatic cases has limited practical value and resources may be better allocated elsewhere— Prof Ooi Eng Eong, Duke-NUS Medical School
Vaccination is the path forward, not as a finish line but as an ongoing tool to reduce severe illness and death— Prof Ooi Eng Eong
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